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four terms, fallacy of
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 Related Terms
fallacy
categorical syllogism
equivocation

 

Definition:
The fallacy of four terms is a formal fallacy which is committed in a categorical syllogism which uses more than the maximum three categorical terms allowed. For example:

All cardinals are animals.
All chickens are birds.
Therefore, all cardinals are animals.

The four terms above are: cardinals, animals, chickens and birds. The above conclusion may be true, but not because of the argument. The fallacy of four terms can also be understood as a form of equivocation, because the syllogism often equivocates on one of the terms, making it look like there are only three. For example:

Only man is born free.
No women are men.
Therefore, no women are born free.

The above looks like it only has three terms: man, free, and woman. However, the term man is being used in two different ways: man as a synonym for humanity, and man as one gender. This, this a both a fallacy of four terms and an example of equivocation.

Also Known As: quaternio terminorum

Alternate Spellings: none

Common Misspellings: none

Related Resources:

What is the Logic and the Philosophy of Language?
The two fields Logic and the Philosophy of Language are often treated separately, but they are nevertheless close enough that they are presented together here. Logic is the study of methods of reasoning and argumentation, both proper and improper. The Philosophy of Language, on the other hand, involves the study of how our language interacts with our thinking.

What is Philosophy?
What is philosophy? Is there any point in studying philosophy, or is it a useless subject? What are the different branches of philosophy - what's the difference between aestheitcs and ethics? What's the difference between metaphysics and epistemology?

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